CN103368896B - A kind of method of carrier auxiliary in high order modulation-demodulation - Google Patents

Abstract

The present invention relates to field of microwave communication, particularly to a kind of method of carrier auxiliary in high order modulation-demodulation.The method by inserting auxiliary sequencel utilize the correlation of auxiliary sequencel to carry out carrier auxiliary, be divided into Clock Extraction, produce timing frame, transmitting-receiving carrier beat recover with compensate, transmitting-receiving carrier phase difference is recovered and compensates and the step such as removal of phase ambiguity.The present invention reuses auxiliary sequencel and carries out related operation, calculates frequency difference, difference, and carries out correlative compensation, and good in anti-interference performance can recover carrier phase in the case of low signal-to-noise ratio reliably, completes signal demodulation, and robustness is high；Symbolization speed during realization, it is achieved relied on hardware platform requirements is relatively low, coding realizes simple.

Description

A kind of method of carrier auxiliary in high order modulation-demodulation

Technical field

The present invention relates to field of microwave communication, particularly to a kind of method of carrier auxiliary in high order modulation-demodulation.

Background technology

Growing along with present communications technology, frequency resource is more and more nervous, and the capacity of legacy communications system is Increasingly can not meet the requirement of user, high order modulation-demodulation is increasingly paid close attention to by people.High order modulation-demodulation can not only The transmission capacity of raising system, and greatly increase the availability of frequency spectrum.The development of digital signal processor and people Interest to the application of broadband wireless field, promotes the quick growth of high order modulation-demodulation technology.Height along with microelectric technique Degree development, by three key technologies (collaborative design technology of soft and hardware, IP module library skill in integrated chip system (SOC) Art, the Comprehensive Analysis Technique between module interfaces) innovations and breakthroughs so that the scale of FPGA is increasing, carries for various algorithms Supply hardware design condition, used FPGA design to have the biggest free degree simultaneously for designer, need not only adhere rigidly to In circuit such as registers.And the fast development of EDA technology makes the checking of many methods can directly utilize computer realization, Provide a great convenience for designer.

In traditional communication system, generally using phaselocked loop to realize carrier synchronization, these methods cannot be used for high order modulation Demodulation.Existing high-order carrier recovering method mostly uses digital processing mode, mainly utilizes open loop frequency algorithm for estimating direct Estimate reception carrier wave and the frequency difference of local carrier, then corrected.Method used mainly has: maximum likelihood parameter Estimation (ML) error estimation algorithm, this algorithm asks likelihood function process complicated, it is achieved get up extremely difficult；Towards judgement (DD) algorithm, This algorithm realizes simple, but carrier wave catching range is less than ± 10kHz, it is impossible to meet the demand of user；RC algorithm, this algorithm is uncomfortable By the 128QAM system not having outer angle point；Polarity decision phase detection algorithm is current most a kind of algorithm, but when frequency The when of the biggest, polarity algorithm becomes extremely complex.

Summary of the invention

For solving the problems referred to above, the invention provides a kind of carrier wave in high order modulation-demodulation realized based on FPGA The method recovered, owing to this carrier recovering method depends on supplemental training sequence (BPSK modulation), so in the feelings of little signal to noise ratio Under condition, the work that this carrier recovering method still can be stable；It is divided into Clock Extraction and frame regularly, greatly because of carrier auxiliary process simultaneously Frequency deviation and little frequency deviation are recovered, difference is recovered three steps and completed, so stable phase shake is little.

For reaching above-mentioned purpose, the technical solution used in the present invention is as follows:

In a kind of high order modulation-demodulation, the method for carrier auxiliary, comprises the steps:

(1) Clock Extraction: utilize Gardner algorithm to extract synchronised clock；

(2) frame timing: utilize auxiliary sequencel to carry out computing cross-correlation, produce various frame timing signal；

(3) transmitting-receiving carrier beat recovers and compensates: utilizes auxiliary sequencel to divide two sections I, Q two-way is carried out related operation and obtains Two correlations, and utilize Cordic algorithm to obtain two phase value Φ of correspondence₁、Φ₂, obtain before and after auxiliary sequencel two sections it Between phase difference ΔΦ, thus calculate the large frequency-difference Δ f of transmitting-receiving carrier wave, recycling auxiliary sequencel computing cross-correlation and frame are fixed Time, calculate little frequency difference Δ β, utilize compensation formula that frequency difference is compensated；

(4) transmitting-receiving carrier phase difference is recovered and compensates: after completing frequency difference compensation, carry out cross-correlation fortune again with auxiliary sequencel Calculate, obtain phase place ρ corresponding to auxiliary sequencel in current demand signal₂, obtaining receiving and dispatching carrier phase difference is Δ ρ=ρ₂-ρ₁, wherein ρ₁ For the phase place corresponding to auxiliary sequencel of making a start, then carry out the compensation differed.

(5) carrier phase ambiguity is removed.

The carrier recovering method used in this method is based on feed forward type open loop structure synchronous method, is divided into five steps to complete Carrier beat and the recovery of difference and compensation.Use Cordic algorithm, obtain the current phase place that each correlation is corresponding, then to phase Potential difference value carries out continuous print moving average.Why use this algorithm, be because it based on feed forward type open loop structure synchronous method, Have that synchronizing speed is fast, the feature of carrier lock wide ranges.It addition, this algorithm structure is simple, operand is little, it is not take up a large amount of Ram space, it is easy to realize in side circuit, beneficially the popularization of technology and application.

Carrier auxiliary of the present invention completes in one piece of fpga chip with the calculating of compensation, Clock Extraction used in the present invention Method is based on Gardner algorithm, and the formula of Gardner algorithm is

$U_t\left(r\right)=Y_I(r-\frac{1}{2})\×\mathrm{Sgn}[Y_I\left(r\right)-Y_I(r-1)]+Y_Q(r-\frac{1}{2})$

$\×\mathrm{Sgn}[Y_Q\left(r\right)-Y_Q(r-1)].$

Gardner algorithm is that a kind of being applicable to limits the BPSK of band, the synchronization timing error detection method of qpsk modulation signal, Require that sampling rate is the twice of character rate.The present invention is directed to the modulation of 128QAM multilevel electrical level, Gardner algorithm is carried out Improving, eliminate high order modulation noise, in order to improve clock phase stability, the sampling rate used is the 4 of character rate Times.After improvement, the formula of Gardner algorithm is $\begin{array}{c}{U}_t\left(r\right)=\{\frac{[Y_I\left(r\right)+Y_I(r-1)]}{2}-Y_I(r-\frac{1}{2})\}\×\mathrm{Sgn}[Y_I\left(r\right)-Y_I(r-1)]\\ +\{\frac{[Y_Q\left(r\right)+Y_Q(r-1)]}{2}-Y_Q(r-\frac{1}{2})\}\×\mathrm{Sgn}[Y_Q\left(r\right)-Y_Q(r-1)]\end{array},$ Hits According to carrying out DC level adjustment in FPGA, extract synchronization timing error signal Ut (r) by FPGA, carry out cumulative mean and obtain Signal E (r), is converted to analog signal by E (r) by analog-digital converter and controls voltage controlled oscillator, thus extract synchronised clock. The method is applicable not only to BPSK, QPSK, and is applicable to various QAM system.The synchronous clock phase shake that the present invention extracts Little, provide good basis for carrier auxiliary.

Concretely comprising the following steps of step (2): utilize the correlation of auxiliary sequencel, carries out computing cross-correlation to auxiliary sequencel, To R (k),Utilize the amplitude characteristic of R (k), to carrying out a square fortune after R (k) delivery value Calculate, obtain M (k), utilize M (k) that frame timing can be obtained.

Step (3) specifically comprises the following steps that

(3-1) whole auxiliary sequencel section is divided into two parts of PN1, PN2, utilizes the computing formula of R (k) in step (2) Carry out computing cross-correlation respectively；

(3-2) R is obtained by the PN1 section sequence computing cross-correlation of auxiliary sequencel₁(k), $R_1\left(k\right)=\underset{k=1}{\overset{N/2}{\mathrm{\Σ}}}r\left(k\right)\×c_k=\underset{k=1}{\overset{N/2}{\mathrm{\Σ}}}{c}_k\×c_k\×e^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k},$ R is obtained by the PN2 section sequence computing cross-correlation of auxiliary sequencel₂(k), $R_2\left(k\right)=\underset{k=\frac{N}{2}+1}{\overset{N}{\mathrm{\Σ}}}r\left(k\right)\×c_k=\underset{k=\frac{N}{2}+1}{\overset{N}{\mathrm{\Σ}}}{c}_k\×c_k\×e^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k},$ Auxiliary sequencel C_kValue is [+A A], amplitude phase Same positive number or negative, so C_K×C_K=A², for certain value, it is set to C, then $R_1\left(k\right)=C\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k},$ $R_2\left(k\right)=C\×e^{j2\mathrm{\π}\×(\frac{N}{2}\×\mathrm{\Δ\θ})}\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}$

(3-3) utilize frame timing, from continuous print code stream, take out computing cross-correlation result R corresponding to PN1, PN2₁(k)、 R₂(k), it is assumed that R₁(k)、R₂Phase value Φ corresponding to (k)₁、Φ₂, then have

${\mathrm{\Φ}}_1={\mathrm{angleR}}_1\left(k\right)=\mathrm{angle}(c\×\underset{K=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})$

${\mathrm{\Φ}}_2={\mathrm{angleR}}_2\left(k\right)=\mathrm{angle}(C\×e^{j2\mathrm{\π}\×(\frac{N}{2}\×\mathrm{\Δ\θ})}\×\underset{K=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k});$

(3-4) utilize full section auxiliary sequencel to obtain the phase difference ΔΦ of before and after two frame, and then try to achieve the big frequency of transmitting-receiving carrier wave Difference

$\mathrm{\Δf}=\frac{\mathrm{\Δ\Φ}}{\frac{N}{2}T}=\frac{\mathrm{\Φ}2-\mathrm{\Φ}1}{\frac{N}{2}T}$

$=\frac{\mathrm{angle}(c\×e^{j2\mathrm{\π}\×\frac{N}{2}\×\mathrm{\Δ\θ}}\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})-\mathrm{angle}(C\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})}{\frac{N}{2}T}$

(3-5) carrying out computing cross-correlation based on whole Nbit supplemental training sequences, each frame obtains a computing cross-correlation Result G (k),Utilize frame timing to find out every frame auxiliary sequencel computing cross-correlation result, depend on Secondary obtain G1 (k), G2 (k), G3 (k), G4 (k) ..., if little frequency difference is Δ β, every frame is Mbit, then

$\mathrm{\Δ\β}=\frac{\mathrm{angle}\left(G_2\left(k\right)\right)-\mathrm{angle}\left(G_1\left(k\right)\right)}{\mathrm{MT}}=\frac{\mathrm{angle}\left(G_3\left(k\right)\right)-\mathrm{angle}\left(G_2\left(k\right)\right)}{\mathrm{MT}}=\·\·\·,$

Little frequency difference Δ β is carried out moving average, obtains a frequency deviation difference the least；

(3-6) combining the large frequency-difference calculated and little frequency difference, carry out frequency difference compensation, compensation formula is

Q_{Exhausted 1}(t)=I_Phase(t)×sinΨ+Q_Phase(t)×cosΨ

I_{Exhausted 1}(t)=I_Phase(t)×ccsΔΨ_ρ-Q_Phase(t)×sinΨ

Ψ=(Δ f+ Δ β) × t.

Specifically comprising the following steps that of step (4)

(4-1) signal h (t) completing frequency difference compensation is carried out computing cross-correlation according to auxiliary sequencel, cross-correlation fortune can be obtained Calculate result y (k), $y\left(k\right)=R\×{\mathrm{\Σ}}_{K=1}^N{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k};$

(4-2) current demand signal auxiliary sequencel mapped phases in planisphere

${\mathrm{\ρ}}_2=\mathrm{angle}\left(y\left(k\right)\right)=\mathrm{angle}(R\×\underset{K=1}{\overset{N}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}),$ Make a start supplemental training sequence mapping at ρ₁Phase place On, the phase difference ρ=ρ of carrier wave can be received and dispatched₂-ρ₁；

(4-3) signal after completing frequency difference compensation being carried out phase compensation again, compensation formula is

Q_Absolutely(t)=I_{Exhausted 1}(t)×sinΔρ+Q_{Exhausted 1}(t)×cosΔρ

I_Absolutely(t)=I_{Exhausted 1}(t)×cosΔρ-Q_{Exhausted 1}(t)×sinΔρ

The present invention reuses auxiliary sequencel and carries out related operation, calculates frequency difference, difference, and carries out correlative compensation, anti-dry Immunity can be good, can recover carrier phase in the case of low signal-to-noise ratio reliably, completes signal demodulation, and robustness is high；Real Symbolization speed during Xian, it is achieved relied on hardware platform requirements is relatively low, coding realizes simple.

Accompanying drawing explanation

Fig. 1 is hardware platform structural representation used herein；

Fig. 2 is by auxiliary sequencel peak-to-peak value schematic diagram after cross-correlation calculation；

Fig. 3 is frame structure schematic diagram；

Fig. 4 is to comprise transmitting-receiving carrier beat and the 128QAM planisphere of difference；

Fig. 5 is to utilize the carrier recovering method illustrated in the present invention, and the signal in Fig. 4 is removed gained after frequency difference and difference The 128QAM planisphere of signal.

Detailed description of the invention

Fig. 1 is the hardware platform structural representation that the present invention is required when implementing, and this hardware platform is mainly by business interface portion Point, monitoring unit, FPGA circuitry, D/A converter, quadrature modulation circuit, orthogonal demodulation circuit, local oscillation circuit, A/D converter group Become.Business information enter map through sampling, tap framing, multilevel coding after FPGA, insert supplemental training sequence, molding filtration, After D/A conversion, carry out orthogonal modulation and become intermediate-freuqncy signal；The modulated intermediate-freuqncy signal received is become I, Q two through quadrature demodulation by receiving end Road orthogonal signalling, after the filtering of low-pass filtered device, carry out differential amplification and deliver to A/D converter.I, Q two-way 10 of A/D output Signal delivers to FPGA unit, after extracting clock, utilizes inserted supplemental training sequence to carry out related operation, produces the timing of various frame Signal.

In a kind of high order modulation-demodulation, the method for carrier auxiliary, comprises the steps:

1, Clock Extraction: extracting synchronised clock based on Gardner algorithm, the Gardner algorithmic formula used is

$U_t\left(r\right)=\{\frac{[Y_I\left(r\right)+Y_I(r-1)]}{2}-Y_I(r-\frac{1}{2})\}\×\mathrm{Sgn}[Y_I\left(r\right)-Y_I(r-1)]$

$+\{\frac{[Y_Q\left(r\right)+Y_Q(r-1)}{2}-Y_Q(r-\frac{1}{2})\}\×\mathrm{Sgn}[Y_Q\left(r\right)-Y_Q(r-1)],$

In FPGA, carry out DC level adjustment by the sampled data of A/D converter, extracted by FPGA same the most again Step signal of timing error Ut (r), carries out cumulative mean and obtains signal E (r), and by analog-digital converter, E (r) is converted to simulation letter Number control voltage controlled oscillator, thus extract synchronised clock.

2, frame timing: utilize auxiliary sequencel (auxiliary sequencel frame structure position relationship as shown in Figure 3) correlation, right Auxiliary sequencel carries out computing cross-correlation, obtains R (k),Then after to R (k) delivery value Carry out square operation, obtain M (k), M (k)=[abs (R (k))]², the time domain peak-to-peak value figure of M (k) is as in figure 2 it is shown, utilize M K () can obtain frame timing.

3, the recovery of transmitting-receiving carrier wave large frequency-difference:

The signal that receiving end receives can be expressed as

R (k)=c_k×e^j2π×θ(k)+ n (k)=c_k×e^j2π×Δf×k+ n (k), wherein c_kBeing the complex-valued data sent, θ (k) is Unknown carrier frequency offset, n (k) is white Gaussian noise, and meets θ (k)～N (0.2 σ²), its homophase and the variance of quadrature component It is σ²。

(1), whole auxiliary sequencel section it is divided into two parts of PN1, PN2, the signal received is carried out computing cross-correlation, fortune Calculation formula is as follows

$R\left(t\right)=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}r\left(t\right)\×c_k=\underset{k=1}{\overset{L}{\mathrm{\Σ}}}{c}_k\×c_k\×e^{j2\mathrm{\π}\×\mathrm{\Δf}\×t}\×g(t-\mathrm{kT}),$ Wherein T is a code-element period, R (t) is sampled for interval with T, obtains R (k),Δ θ=Δ f × T, R in formula K () represents the computing cross-correlation operation result at kth signal sampling point.

(2), according to the auxiliary sequencel inserted of making a start, the PN1 section sequence computing cross-correlation of auxiliary sequencel R is obtained₁ (k), $R_1\left(k\right)=\underset{k=1}{\overset{N/2}{\mathrm{\Σ}}}r\left(k\right)\×c_k=\underset{k=1}{\overset{N/2}{\mathrm{\Σ}}}{c}_k\×c_k\×e^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k},$ By the PN2 section sequence computing cross-correlation of auxiliary sequencel Obtain R₂(k), $R_2\left(k\right)=\underset{k=\frac{N}{2}+1}{\overset{N}{\mathrm{\Σ}}}r\left(k\right)\×c_k=\underset{k=\frac{N}{2}+1}{\overset{N}{\mathrm{\Σ}}}{c}_k\×c_k\×e^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k},$ Make A_K=C_K×C_K, then haveAgain because of supplemental training sequence C_kValue is [+A A], positive number that amplitude is identical or negative, So A_KFor certain value, it is set to C, then

$R_2\left(k\right)=C\×\underset{K=\frac{N}{2}+1}{\overset{N}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}=C\×\underset{k=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×(\mathrm{\Δ\θ}\×k+\frac{N}{2}\×\mathrm{\Δ\θ})}$

$=C\×e^{j2\mathrm{\π}\×(\frac{N}{2}\×\mathrm{\Δ\θ})}\×\underset{K=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}$

(3), utilize frame timing, from continuous print code stream, take out computing cross-correlation result R corresponding to PN1, PN2₁(k)、R₂ (k), it is assumed that R₁(k)、R₂Phase value Φ corresponding to (k)₁、Φ₂, then have

${\mathrm{\Φ}}_1=\mathrm{angle}{R}_1\left(k\right)=\mathrm{angle}(C\×\underset{K=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})$

${\mathrm{\Φ}}_2=\mathrm{angle}{R}_2\left(k\right)=\mathrm{angle}(C\×e^{j2\mathrm{\π}\×\left(\frac{N}{2}\mathrm{\Δ\θ}\right)}\×\underset{K=1}{\overset{\frac{N}{2}}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}).$

(4), full section auxiliary sequencel is utilized to obtain the phase difference ΔΦ of before and after two frame, because the computing cross-correlation of two PN sequences is tied Fruit N/2 code-element period of difference, tries to achieve the large frequency-difference of transmitting-receiving carrier wave

$\mathrm{\Δf}=\frac{\mathrm{\Δ\Φ}}{\frac{N}{2}T}=\frac{\mathrm{\Φ}2-\mathrm{\Φ}1}{\frac{N}{2}T}$

$=\frac{\mathrm{angle}(C\×e^{j2\mathrm{\π}\×\frac{N}{2}\×\mathrm{\Δ\θ}}\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})-\mathrm{angle}(C\×{\mathrm{\Σ}}_{K=1}^{\frac{N}{2}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k})}{\frac{N}{2}T}.$

4, the recovery of the transmitting-receiving little frequency difference of carrier wave:

Carrying out computing cross-correlation based on whole Nbit supplemental training sequences, each frame obtains a computing cross-correlation Result G (k),Frame timing is utilized to find out every frame auxiliary sequencel computing cross-correlation knot Really, G1 (k), G2 (k), G3 (k), G4 (k) are obtained successively ..., if little frequency difference is Δ β, every frame is Mbit, then $\mathrm{\Δ\β}=\frac{\mathrm{angle}\left(G_2\left(k\right)\right)-\mathrm{angle}\left(G_1\left(k\right)\right)}{\mathrm{MT}}=\frac{\mathrm{angle}\left(G_3\left(k\right)\right)-\mathrm{angle}\left(G_2\left(k\right)\right)}{\mathrm{MT}}=\·\·\·,$ Little frequency difference Δ β is entered Line slip is average, obtains a frequency deviation difference the least.

5, transmitting-receiving carrier beat compensates: combining the large frequency-difference and little frequency difference calculated, carry out frequency difference compensation, compensation formula is

Q_{Exhausted 1}(t)=I_Phase(t)×sinψ+Q_Phase(t)×cosψ

I_{Exhausted 1}(t)=I_Phase(t)×coSΔψρ-Q_Phase(t)×SinΨ

ψ=(Δ f+ Δ β) × t.

1, the recovery of transmitting-receiving carrier phase difference:

(1) signal h (t) completing frequency difference compensation is carried out computing cross-correlation according to auxiliary sequencel, computing cross-correlation can be obtained Result y (k), $y\left(k\right)=R\×{\mathrm{\Σ}}_{K=1}^N{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k};$

(2) current demand signal auxiliary sequencel mapped phases in planisphere

${\mathrm{\ρ}}_2=\mathrm{angle}\left(y\left(k\right)\right)=\mathrm{angle}(R\×\underset{K=1}{\overset{N}{\mathrm{\Σ}}}{e}^{j2\mathrm{\π}\×\mathrm{\Δ\θ}\×k}),$ Make a start supplemental training sequence mapping at ρ₁Phase place On, the phase difference ρ=ρ of carrier wave can be received and dispatched₂-ρ₁;

7, transmitting-receiving carrier phase difference compensates: again carrying out phase compensation to completing the signal after frequency difference compensates, compensation formula is

Q_Absolutely(t)=I_{Exhausted 1}(t)×sinΔρ+Q_{Exhausted 1}(t)×cosΔρ

I_Absolutely(t)=I_{Exhausted 1}(t)×cosΔρ-Q_{Exhausted 1}(t)×sinΔρ

8, carrier phase ambiguity is removed.

Carry out soft-decision, Viterbi decoding, caching, second judgement after signal equalised device equilibrium after compensation, be multiplexed to Frame, it is ultimately routed to business interface unit.

Signal in Fig. 4, after the method described in this invention carries out carrier auxiliary and compensates, eliminates transmitting-receiving carrier wave Frequency difference and difference, finally obtained signal constellation (in digital modulation) figure is as shown in Figure 5.

Claims (5)

1. the method for carrier auxiliary in a high order modulation-demodulation, it is characterised in that comprise the steps:

(1) Clock Extraction: utilize Gardner algorithm to extract synchronised clock；

(2) frame timing: utilize auxiliary sequencel to carry out computing cross-correlation, produce various frame timing signal；

(3) transmitting-receiving carrier beat recovers and compensates: utilizes auxiliary sequencel to divide two sections I, Q two-way is carried out related operation and obtains two Correlation, and utilize Cordic algorithm to obtain two phase value Φ of correspondence₁、Φ₂, obtain before and after auxiliary sequencel between two sections Phase difference ΔΦ, thus calculate the large frequency-difference Δ f of transmitting-receiving carrier wave, recycling auxiliary sequencel computing cross-correlation and frame timing, meter Calculate little frequency difference Δ β, utilize compensation formula that frequency difference is compensated；

(4) transmitting-receiving carrier phase difference is recovered and compensates: after completing frequency difference compensation, carry out computing cross-correlation again with auxiliary sequencel, Obtain phase place ρ corresponding to auxiliary sequencel in current demand signal₂, obtaining receiving and dispatching carrier phase difference is Δ ρ=ρ₂-ρ₁, wherein ρ₁For sending out End phase place corresponding to supplemental training sequence, then carries out the compensation differed；

(5) carrier phase ambiguity is removed.

The method of carrier auxiliary in high order modulation-demodulation the most according to claim 1, it is characterised in that above steps exists Completing in fpga chip, wherein in step (1), the formula of Gardner algorithm is:

Wherein, r refers to sampling instant；Y_IR () refers to the I road signal sampled value in the r moment；Y_I(r 1) refers to that I road signal is at (r- 1) sampled value in moment；Refer to that I road signal existsThe sampled value in moment；In like manner Y_Q(r)、Y_Q(r-1)、Q road signal respectively the r moment,Moment, the sampled value in (r-1) moment；Sampled data is entered in FPGA Row DC level adjusts, and extracts synchronization timing error signal U by FPGA_tR (), carries out cumulative mean and obtains signal E (r), by E R () is converted to analog signal by analog-digital converter and controls voltage controlled oscillator, thus extract synchronised clock.

The method of carrier auxiliary in high order modulation-demodulation the most according to claim 1, it is characterised in that step (2)

Concretely comprise the following steps: utilize the correlation of auxiliary sequencel, auxiliary sequencel carried out computing cross-correlation, obtains R (k),

Wherein, L refers to the he number of auxiliary sequencel；K refers to sampling instant；c_kRefer to kth signal in the auxiliary sequencel sent Sample value；Δ θ is the difference between former and later two code elements；R (k) is that the signal of reception is carried out the result that computing cross-correlation obtains； Utilize the amplitude characteristic of R (k), carry out square operation to after R (k) delivery value, obtain M (k), utilize M (k) that frame can be obtained fixed Time.

The method of carrier auxiliary in high order modulation-demodulation the most according to claim 3, it is characterised in that step (3) concrete Step is as follows:

(3-1) whole auxiliary sequencel section is divided into two parts of PN1, PN2, utilizes the computing formula of R (k) in step (2) respectively Carry out computing cross-correlation；

(3-2) R is obtained by the PN1 section sequence computing cross-correlation of auxiliary sequencel₁(k),

R is obtained by the PN2 section sequence computing cross-correlation of auxiliary sequencel₂(k),

In formula, r (k) is to terminate, at k reception, the signal received, and its amplitude is equal to c_k, phase offset is 2 π × Δ θ × k, institute There to be r (k)=c_k×e^{j2π×Δθ×k}；Auxiliary sequencel c_kValue is [+A, A], positive number that amplitude is identical or negative, so c_k×c_k =A²For certain value, it is set to C, then has:

(3-3) frame timing is utilized, result R that taking-up auxiliary sequencel section PN1, PN2 computing cross-correlation obtain from continuous print code stream₁ (k)、R₂(k), it is assumed that R₁(k)、R₂K the phase value corresponding to () is respectively Φ₁、Φ₂, then have:

(3-4) the phase value Φ that auxiliary sequencel section computing cross-correlation result is tried to achieve is utilized₁、Φ₂, obtain auxiliary sequencel section further Phase difference ΔΦ between PN1 and PN2, ΔΦ=Φ₂-Φ₁, owing to the computing cross-correlation of two auxiliary sequencel sections PN1, PN2 is tied Fruit front and back differs in sequentialIndividual code element, it is thus possible to obtain the large frequency-difference of transmitting-receiving carrier wave

Wherein, N refers to the he number of whole auxiliary sequencel；K refers to sampling instant；c_kRefer to that the auxiliary sequencel sent is when kth The sampled value carved；Δ θ is the difference between former and later two code elements；T refers to the cycle of symbol code element；Φ₁It it is auxiliary sequencel section PN1 The phase value that computing cross-correlation result is corresponding；Φ₂It is phase value corresponding to auxiliary sequencel section PN2 computing cross-correlation result,

(3 5) auxiliary sequencel based on whole Nbit carries out computing cross-correlation, and each frame obtains computing cross-correlation result G (k),

Utilize frame timing to find out every frame auxiliary sequencel computing cross-correlation result, obtain G successively₁(K)、G₂(K)、G₃(K)、G₄(K) ..., If little frequency difference is Δ β, every frame is Mbit, then have:

Little frequency difference Δ β is carried out moving average, obtains a frequency deviation difference the least,

(3-6) utilizing the large frequency-difference calculated and little frequency difference, carry out frequency difference compensation, compensation formula is:

Q_{Exhausted 1}(k)=I_Phase(k)×sinΨ+Q_Phase(k)×cosΨ

I_{Exhausted 1}(k)=I_Phase(k)×cosΔΨρ-Q_Phase(k)×sinΨ

Wherein Ψ=(Δ f+ Δ β) × T, I_PhaseK () refers to the sampled value at k reception I road signal；Q_PhaseK () referred in the k moment Receive the sampled value of Q road signal；I_{Exhausted 1}K () refers to the I road signal recovered after the k moment carries out frequency difference compensation；Q_{Exhausted 1}K () refers at k Moment carries out the Q road signal recovered after frequency difference compensation.

The method of carrier auxiliary in high order modulation-demodulation the most according to claim 4, it is characterised in that step (4) concrete Step is as follows:

The signal completed after frequency difference compensates is carried out computing cross-correlation according to auxiliary sequencel by (4 1), can obtain computing cross-correlation knot Really y (k),

(4 2) current demand signal supplemental training sequence mapped phases in planisphere is ρ₂,

Owing to making a start, auxiliary sequencel is mapped in ρ₁In phase place, so the phase difference ρ=ρ of transmitting-receiving carrier wave₂-ρ₁,

(4 3) carry out phase compensation again to completing the signal after frequency difference compensates, and compensation formula is:

Q_Absolutely(k)=I_{Exhausted 1}(k)×sinΔρ+Q_{Exhausted 1}(k)×cosΔρ

I_Absolutely(k)=I_{Exhausted 1}(k)×cosΔρ-Q_{Exhausted 1}(k)×sinΔρ

I_{Exhausted 1}K () refers to the I road signal recovered after the k moment carries out frequency difference compensation；Q_{Exhausted 1}K () refers to carry out frequency difference compensation in the k moment The Q road signal of rear recovery；I_AbsolutelyK () refers at the I road signal that the k moment finally recovers；Q_AbsolutelyK () refers at the Q that the k moment finally recovers Road signal, thus obtained the signal R (K), R (k)=I after frequency difference, difference compensation_Absolutely(k)+Q_Absolutely(k)。